Scabies

What is it?

Scabies, also called the "seven-year itch," is caused by the burrowing mite Sarcoptes scabiei. Female mites are turtle-shaped and about 0.4 mm long (about 1/50 inch), with four pairs of legs. They burrow into the top layer of human skin to lay their eggs, which hatch within two weeks.

Scabies mites are usually transmitted from person to person by close bodily contact, especially among family members, persons who share the same bed or clothing, or sexual partners. Mites can live for two days to three days in clothing, bedding, or dust. In specific cases, casual contact may spread the infection. Children under age 15 are more likely to catch scabies. A child may increase the risk of getting scabies by borrowing other children's clothing.

What are the symptoms?

Scabies is an infection that affects the skin. The most common symptom of scabies is itching, which may be worse at night or after a hot bath. A scabies infection begins as small, itchy blisters that break when your child scratches them. Itchy skin may become thick, scaly, and crisscrossed with scratch marks. Because scabies is caused by a mite that burrows into the top layer of skin, you may actually see the mite's burrows as short, dark, wavy lines on the skin's surface.

The arms and hands are the areas of the body that are most commonly affected by scabies, especially the webs of skin between the fingers, the inner part of the wrists, and the folds under the arms. If the scabies infection is severe, other areas of the body may also be affected, particularly the elbows and the areas around the breasts (in older girls), genitals, navel, and buttocks. In older children and adults, the face, head, palms, and soles are usually spared. In infants, almost any area of the skin can be involved.

When children scratch the itchy areas of skin affected by scabies, they increase the chance that the injured skin will also be infected by bacteria. Impetigo, a skin infection caused by another germ, the streptococcus bacteria, may occur in skin that is already infected with scabies.

How is it treated?

If your child's doctor suspects that your child has scabies, he or she may scrape a small part of the affected skin and examine the scrapings under a microscope for signs of scabies mites.

In older children and adults, scabies is treated by applying a prescription cream or lotion of gamma benzene hexachloride (also called GBH, Gamene, or Kwell), which is a weak solution of the pesticide lindane. This medication usually must remain on the skin for several hours before it can be washed off, and it should not touch the eyes or mucous membranes. Other medicines that may be used include crotamiton or benzyl benzoate.

Infants and pregnant women with scabies may absorb dangerous amounts of GBH through their skin. In these patients, doctors may treat scabies with different types of medications, often containing sulfur.

Because scabies can be sexually transmitted, sexually active older children with scabies may need to be examined for other sexually transmitted diseases.

Children who have developed a bacterial skin infection such as impetigo in addition to the scabies infection may need an antibiotic prescription as well. Your child's doctor may also prescribe an antihistamine to treat itching.

How long do the symptoms last?

Once a person starts receiving treatment for scabies, it usually takes about two hours to four hours to become noninfectious (no longer able to spread infection to others). Itching generally stops soon after treatment begins, but it can also continue as part of an allergic reaction that may last for weeks. The skin marks of scabies usually clear in one week to two weeks, but in some children they take up to two months to disappear.

When is it over?

Once a scabies mite lays eggs under the skin, it takes about two weeks for young mites to hatch.

How can my child get it?

Scabies is a contagious disease caused by a mite. It is spread from person to person by close physical contact (including sexual activity) and by sharing the same bed, linens, clothing, or towels.

How can it be prevented?

Scabies may be prevented by practicing good hygiene. Some good habits to encourage include daily showers or baths (or at least two times to three times a week); frequent hand washing, especially before eating; and wearing clean clothing. Encourage your child not to share clothing with friends.

Once someone in your family is being treated for scabies, all other household members should be treated, too. Clothing and bed linens used before treatment started should be washed in hot water.

When should the doctor be called?

Call your child's doctor whenever your child has a skin itch that will not go away, especially if the itch is worse at night and seems to center around the wrists or the webbed part of the fingers.

Also call your child's doctor for any of the following skin symptoms: blisters, rash, red streaks or lines, pain, pus, or swelling.

How is it treated at home?

If your child has scabies, you may need to help her apply the medicine prescribed by your doctor. This usually involves applying the medicine to your child's skin, covering her entire body from the neck down, and leaving the medicine on for several hours. All other household members will need treatment as well. If scabies affects an older child who is sexually active, the sexual partner will also need treatment for scabies.

All clothing, towels, and bed linens will need to be washed in hot water. Your child's toys should also be washed, but there is no special cleaning needed for floors or furniture.
© Copyright 1999 American Medical Association
All rights reserved.